In this photo instructable you will learn about the diode and build a simple circuit that helps you understand how a diode works using Snap Circuits.
Snap Circuits is an educational toy that teaches electronics with solderless snap-together electronic components. Each component has the schematic symbol and a label printed on its plastic case that is color coded for easy identification. They snap together with ordinary clothing snaps. The components also snap onto a 10 X 7 plastic base grid analogous to a solderless breadboard. There are several Snap Circuits kits that range from a few simple circuits to the largest kit that includes 750 electronic projects.
All the kits include manuals printed in color with easy to follow diagrams to assemble the projects. The illustrations for each project look almost exactly like what the components will look like on the base grid when finished. Because the electronic symbol is printed on each electronic component, once the project is completed, it will look almost exactly like an electronic schematic.
I like to use Snap Circuits to demonstrate electronic circuits because it is easy for you to understand whatís going on in a circuit as you learn by doing, that is, you learn about electronics by actually building the circuits.
1 Battery Holder (2-AA) # 6SC B1
1 Base Grid (11" x 7.7") # 6SC BG
1 SPDT Switch # 6SC S5
1 Diode 1N4001 # 6SC D3
1 2.5V Lamp Socket (With Bulb) # 6SC L1
2 Conductor with 2-snaps # 6SC 02
Parts can be ordered from C&S Sales (http://cs-sales.net/sncirepa.html)
According to Wikipedia, "The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward direction), while blocking current in the opposite direction (the reverse direction). Thus, the diode can be viewed as an electronic version of a check valve." (http://en.wikipedia.org/wiki/Diode)
What is a check valve? You can think of it like a ping pong ball cage snorkel. When the ping pong ball cage is above the surface of the water, the ping pong ball is at the bottom of the cage and you can breathe through the snorkel. As the cage moves below the surface of the water, the ping pong ball floats up until it blocks the opening of the snorkel blocking any water from getting into the snorkel. (see picture 2)
The diode has a number of applications in electronic circuits. One application you may be familiar with is a rectifier. A rectifier converts Alternating Current (AC) to Direct Current (DC). Alternating Current periodically changes direction while Direct Current only flows in one direction.
To use a diving analogy, imagine a scuba diver. Since scuba divers carry their air with them they can still breathe whether their heads are above water or underwater. You can imagine a scuba diver surfacing and diving repeatedly and the path he traces forms a sine wave like the one in picture 3.
The sine wave is what Alternating Current looks like. At the crest, or top of the wave you might measure +5 volts and at the trough, or bottom of the wave you might measure -5 volts. At the line through the middle you would measure 0 volts. (see picture 4)
Letís say we wanted to use a diode as a rectifier to convert Alternating Current to Direct Current. Now imagine our snorkeler surfacing and diving. While the ping pong ball cage on the snorkel is above the water the snorkeler can take a breath of air. When the cage sinks below the water the ping pong ball blocks the water from getting into the snorkel and the snorkeler has to hold his or her breath until surfacing again to exhale and take another breath. Like the ping pong ball acts as a check valve to prevent water from getting into the snorkel, the diode acts as a check valve to block the voltage from flowing in the reverse direction.
Picture 5 is what the voltage will look like when the Alternating Current is converted to Direct Current. You would measure from 0 volts to +5 volts then back to 0 volts. You wouldn't be able to measure the voltage reverse direction from 0 volts to -5 volts because it is being blocked by the diode. When the Alternating Current cycles back to 0 volts you would then be able to measure the voltage from 0 volts to +5 volts and then back to 0 volts.
Build a simple circuit to understand how the diode stops current from flowing in the wrong direction
Now we can see what happens when we reverse the diode. Pictures 6 and 7 demonstrate the build of the circuit with the diode in reverse direction. Notice too that that the switch on the S5 block is set to the "B" position, or off. Picture 8 shows what happens when we switch the circuit on, or move the switch from the "B" position to the "A" position...well, nothing happens.
In a DC (direct current) circuit where the electricity can only flow in one direction, we can think of a battery as a storage tank like the water tower in your neighborhood. If nobody turned on their faucet, the water in the tower would just sit there. Forever. Physicists like to think of this as "potential energy." Like a boulder at the top of a hill, it will just sit there, forever, until someone pushes it over the hill or an earthquake shakes it from the top of the hill or erosion undermines it starting it to roll down the hill. When the boulder is rolling down the hill, physicists like to think of this as kinetic energy. So, the water will just sit in the top of the water tower until you turn on the faucet to your water hose. The water will then flow from the top of the water tower through your water hose and then on to the ground. You can then think of the flow of water as kinetic energy and this kinetic energy can be used to do useful work. See picture 9.
When no circuit is connected to your battery, it is like a storage tank, or potential energy. When a circuit is connected to your battery you can think of it as electrons flowing from the positive side of the battery (marked with a "+" sign) to ground (marked with a "-" sign) and you can think of the flow of electrons as kinetic energy that can be used to do useful work such as light up an incandescent bulb.
So, when you switch the circuit on, why doesn't the light bulb light up? Because the diode is blocking the flow of electrcity Like when you put a kink in your waterhose which will stop the flow of water out of the hose and onto the ground.
Switch the circuit off and change the diode from the reverse direction to the forward direction. Then switch the circuit on and the light bulb lights up. (See picture 10)
Now the diode is no longer blocking the flow of electricity and the electrons can flow from the positive (+) terminal on the battery through the circuit to the ground (-) terminal on the battery.
Picture 10 is the electronic symbol for the diode so that you will be able to recognize it on an electronic schematic.